This exercise is inspired by the article which discuss how the Korean War could have been different. (Jerry D. Morelock, "Hard Choices: Truman's Dilemma," Armchair General Volume 5 #2 May 2008) The article discuss three options Truman had after Inchon landing: maintain status quo at 38th Parallel, ordering the advance up to Yalu River, or creating new DMZ north of Pyongyang and Wonsan. This article will explore the possibility of the third option, and probable impact of the outcome.

Background:

Korean Peninsula is orphan of the post WWII policies. Issue of Korean independence among Allies nations was first raised during the Cairo Conference. Chiang Kai Shek of the Nationalist China advocated immediate independence of Korea after the cessation of hostility. [Whose patronage to Korean Provisional Government (Korean government in exile) began when Korean terrorist attacked Japanese delegates who were celebrating victory over the Chinese in the immediate aftermath of the Battle of Shanghai. Chiang Kai Shek praised the
action as "more effective than one million soldiers."] Churchill confess he doesn't know where Korea is while Roosevelt recommend trusteeship. Allied leaders never discussed the Korean issue in detail afterward. Korean policy will be dormant until the aftermath of the Yalta Conference. Eager to involve Soviet Union into the war against Imperial Japan, Roosevelt secured promise from Stalin that Soviet will declare war against Japan three months after Germany surrendered.

Stalin asked three months since he needs time to redeploy his armies from Europe to East Asia. On August 20, 1945, Soviet launched Operation August Wind against Imperial Japanese forces in Manchuria, Korea, Sakhalin and Kurils.

As Soviet forces pressed southward down the Korean peninsula, American leaders insist on the Soviet leaders to cease the advance at the 38th Parallel.

Americans chose the parallel as simple expedient, it is north of Seoul and Pusan, but they are ignorant of historical implication. At the beginning of the 20th Century, then Imperial Russia suggest to Japan a compromise over issue of colonial influence on Korea: territory north of 38th Parallel is to be under the Russian, while territory in the south will belong to Japan. Japan refused and waged Russo-Japanese War. To the Soviet, Americans are acquiescing the control of Korea north of 38th to them, while Americans simply thought of as temporary matter.

This is further complicated by American handling of dialogue with Koreans. Many Koreans advocate immediate sovereign government. Americans insist issue be discussed later. Worse, Americans employed Koreans who collaborated with Japanese colonial government in handling every day issue. This created anger and hostility that leads to death of about 100,000 Koreans by the time Korean War begin.

This is exasperated by aggressive posture by Rhee Syngman, president of newly created Republic of Korea in 1948. Rhee threatened to invade North Korea and encouraged RoK units near the 38th Parallel to clashed with Korean People's Army (KPA or Inmingun). This led to curtail of number and types of armament Americans were willing to give to South Korean army. Thus when Korean War start, RoK Army is underequipped for war.

Another blunder is news article that stated that Secretary of State Acheson declares South Korea is outside of American responsibility. The report is in error since Acheson in interview stated that South Korea is under American sphere of protection. The road to war in Korea was paved with mistakes in fact. In the early morning of June 25, 1950, North Korean military, Korean People's Army, or aka Inmingun, crossed the 38th Parallel.

Fork on the Road:

After Inchon Landing, President Truman and American Chief of Staff debated whether to cross the 38th Parallel. By recapturing Seoul, American military and UN forces are nearly fulfilling the UN mission to force North Koreans out of South Korea. But should they cross the border? After much discussion and consultation with MacArthur and unauthorized crossing by South Korean military, police and militia, Truman permitted the UN forces to cross the 38th Parallel under UN Resolution.

(Retrieved from http://en.wikipedia.org/wiki/UN_Offensive,_1950 on July 21/2009).

Originally, as the UN Forces surge upward pass the 38th Parallel, MacArthur planned to stop his forces south of Yalu: initially drawing the line at Chonhju to Jungnam and later revised to be at Songchon-Songjin.

(D. Clayton James, "Refighting the Last War: Command and Crisis in Korea 1950 -
1953" The Free Press, NY 1993 p193) These lines has the most favorable
defensive terrain and frontline length, roughly 100 miles wide. According to then military manual, a division should defend a front six to eight miles wide.
(Donald W. Boose Jr. "US Army Forces in the Korean War 1950-53" Osprey Publishing, 2005 p40).

These tactical advantage is recognized not only by the American Chief of Staff but also by the British. (Roy Appleman, "Disaster in Korea: Chinese Confront MacArthur," Texas & M University Press, 1989, p341).

British minister Bevin further propose a demilitarized Korean-Chinese border to assure the Chinese that conflict in Korea will not spread to China. Even the
journalist advocate the stop. (Appleman, p345).

Called the "Waist" of Korea by Appleman, that part of the region is crossed by 39th Parallel. (Appleman, p343). From coast west of Pyongyang to Wonsan, the waist is 100 miles wide, and by road used to cross it is 140 miles long. It was practical to stop at 39th Parallel, since nearly all the Korean population and infrastructure are concentrated in the south of the 39th and it is natural chokepoint for all communication network that run up and down the Korean peninsula.

At the time of the push, six of the eight South Korean divisions were advancing with the UN Forces: I Corps with Capital and 3rd Division, II Corps with 6th, 7Th and 8th Divisions, and 1st Division with US I Corps. (Nigel Thomas, etc "The Korean War 1950-53" Osprey Publishing, 1986 p11)
The III Corps with 5th and 11th Divisions were assigned to security duties.
Backing the Republic of Korea Army is the United States military, which provides nine divisions and three corps. (ibid, p16) Hence total of 15 divisions are at MacArthur's disposal as they were advancing toward Yalu.

Had MacArthur kept to his original plan and halted his units at Songchon-Songjin line, each division would have 6 and 2/3 mile front, reasonably within contemporary military doctrine. Slightly longer than 10 km, some units like the South Korean may face difficulty defending such frontage.
But with adequate fire support and lack of gap between units may have compensated the weaknesses that forced the US led UN forces to retreat in actual event.

Analysis

Could the UN forces, under strategic command of MacArthur and tactical command of Walker, hold the line at the 39th Parallel? Walker had prepared contingency plan to hold the line at 39th Parallel. (Appleman p350). Had the American officers knew logistical weaknesses of Chinese military, and the X Corp not mauled by the Chinese offensive as they were advancing north of 39th Parallel in actual event, and establish line similar to Hindenburg Line north of Pyongyang, the UN force could have hold at 39th Parallel. (Appleman, p353).

Other problems the UN forces would have if they hold the line would have been solved in time.

The mountain region that bisect across the 39th Parallel would have been
difficult but the Chinese and KPA had proven during actual war not impossible to cross.
(Appleman, p344). Further UN forces will have access to Wonsan and Chinnampo,
port southwest of Pyongyang, as logistical depots. Remnants of KPA are conducting guerilla warfare behind UN line and is causing terrible havoc. But
had the UN forces stopped at 39th Parallel and held the line, these forces
would have been eventually destroyed in counterinsurgency campaign as happened in actual war.

What would happened had the line held at 39th Parallel? Possibilities are staggering. By placing DMZ at 39th Parallel instead of 38th Parallel, China will be content since they still have buffer zone between itself and Western forces. More importantly, Chinese will have stronger influence on Communist Korea. During the actual Korean War, pro-Chinese faction of Korean Communist Party were purged by Kim Il Sung. Had 39th Parallel as DMZ happened, this faction would have stayed intact or rebuilt. This is so since nearly all the Korean population is located south of alternate DMZ, so the Inmingun wont have the manpower to guard the DMZ. In actual history, the KPA maintain an army of around 300,000 until 1980s, compared to RoK military manpower of 650,000 in late fifties and around 500,000 for past fifty years. This mean that Chinese must maintain a permanent garrison north of DMZ. Thus Communist Korea will suffer presence of foreign troops as the South Korea will: oversexed, overbearing and over here.

Althought timeline of economic miracle the Republic of Korea enjoyed will probably be the same, but they will enjoy more resources and manpower than now. Which means RoK will more economically robust than it is now, since technically it is an unified country in all but in name.

As China goes into transformation under Deng Xiaopeng, the Chinese will force Communist Korea to do same. And the Communist Korea, because of presence and need of Chinese military in Korea, will acquiescened. This mean Korea peninsula may united under Taegukki by mid to late 1990s, a possibility, under a condition favorable to China of course.